A visitor to Zion National Park who was canyoneering in the popular "Subway" section died when his foot became trapped on a descent, according to a park release.

Park officials say the unidentified victim and a partner had a permit to descend through the Subway on Tuesday. The two, who were unfamiliar with the backcountry route, were the last to head down it on Tuesday.

"On the last rappel, the victim got his foot caught and could not free himself. His partner, who had already descended, was unable to help from below," said the release. "The partner was caught by darkness and was unfamiliar with the exit route, and could not make it out of the canyon until Wednesday morning to alert park rangers."

The release did not mention how the fatality occurred. Calls to the park Thursday for additional details were not immediately returned.

The Subway is Zion National Park's most popular canyoneering route and requires several rope rappels. This is the first death in the Subway in recent history, but there are a number of rescues annually, according to park personnel.

"The Subway is deceiving. It is a very popular trail, but very difficult- the 9-mile hike requires rappelling and ascending skills, extensive route finding experience, and swimming through several cold and deep pools," said Zion Superintendent Jock Whitworth. "Unfortunately, its location inside the wilderness also means that rescues are not always possible or timely enough. Sound decision-making and problem solving are critical."